1. Field of the Invention
The present invention relates to oil field tools. More specifically, the invention relates to an apparatus for and a method of using a sealing member, such as a valve, disposed in a wellbore.
2. Background of the Related Art
Oil field wells are drilled typically using a tubular drill string attached to a drill bit to a subterranean producing zone to form a wellbore. Drilling fluid is flowed downhole through the interior of the drill string, through ports, for example, in a drill bit (not shown) to wash away debris at the cutting surfaces, and then upward through an annulus formed between the drill string and a tubular casing that lines the wellbore. The casing is perforated to allow production fluid to flow into the casing and up to the surface of the well, and the drill string is removed from the wellbore.
During drilling, regions of the wellbore are sometimes sealed from other regions. For example, various oilfield equipment, such as motion compensators, periodically need resetting or adjusting in the wellbore. The drill string is plugged and the drilling fluid is raised to a given pressure to actuate or reset the equipment. In other instances, control of the well can be lost due to excessive pressure through the wellbore from subterranean zones. The drill string can become damaged and require repair. The drill string may need temporary plugging below the damage. In other instances, the drill pipe can be temporarily plugged to restrain any flow of production fluid through the drill pipe while zones in the drill string above the plug are tested.
A typical apparatus used to seal between two regions of the drill string is known as a bridge plug and typically includes slip elements and packer elements. The slip elements are used to grip the inside surface of the drill string or other surfaces, thereby preventing the bridge plug from moving up or down in the drill string. The packer elements engage the inside surface of the drill string or the wellbore to provide the requisite seal. The drilling must be stopped to set the retrievable bridge plug, portions of the drilling operation are disassembled, and wireline tools and a bridge plug are inserted into the drill string to an appropriate depth to provide a seal between two zones in the drill string. One type of bridge plug is a permanent bridge plug that can be set in place against a surface, such as an inside surface of a drill string. However, the bridge plug typically is removed by drilling or milling through the plug, which can be costly and time consuming. Another type of plug is a retrievable bridge plug, which typically uses hydraulic fluid to selectively actuate the slip elements and packer elements. The retrievable bridge plug can be removed by releasing pressure on the elements and pulling the bridge plug from the wellbore. Either type of bridge plug needs subsequent removal to provide fluid flow to lower regions or for access with downhole tools. The removal can involve several steps and can be expensive and time consuming. It would be advantageous to be able to be repetitively seal the wellbore or other passageway with an apparatus without necessitating having to drill or mill through the apparatus or to pull the apparatus for removal.
There remains a need for an improved system and method for sealing a drill string that can remain in the wellbore for subsequent use.
The present invention generally provides a system and method for selectively sealing a drill string or other tubular member. In one aspect, a sealing member, such as a valve, allows a certain level of flow of drilling fluids and/or other fluids through one or more flow channels when the valve is open. To close the valve, the flow rate is increased so that a backpressure develops and urges the valve to a closed position. The valve can remain in position in the drill string and alternately open and close depending on the flow rate and/or the pressure drop through the valve. The valve also comprises a removable plug disposed in the valve to provide access with, for example, wireline tools to a region below the valve in a wellbore.
In one aspect, a system for sealing a wellbore comprises one or more such as tubular members, such as drill pipe, one or more flow actuated shut-off valves coupled to the one or more tubular members, at least one source of fluid coupled to the one or more tubular members, and at least one pressure source coupled to the source of fluid. In another aspect, a flow actuated shut off valve comprises a body, a piston disposed in the body, one or more channels disposed through the piston having an inlet to the piston and an outlet from the piston, and a bias member coupled to the piston. In another aspect, a method of closing an oilfield valve comprises flowing a first fluid through a valve at a first flow rate, flowing the first fluid through the valve at a higher second flow rate, at least partially closing the valve with a force exerted by the second flow rate.